1. Field of the Invention
The present invention relates to optical connectors and, especially, to an optical connector having an improved stop ring.
2. Description of the Related Art
A conventional optical connector will be described below. As FIG. 7(a) shows, an optical fiber cable 10 comprises a fiber element 11, a core wire 13, a braid 15, and a sheath 17. When the optical fiber cable 10 is attached to a connector, a variety of components are attached to the optical fiber cable 10. Different lengths of the sheath 17, braid 15, and core wire 13 are removed in order to expose the fiber element 11, core wire 13, and braid 15. Then, as FIG. 7(b) shows, a ferrule 19 is attached to a front end of the optical fiber cable 10 before components of the connector are attached. FIG. 8 shows the optical fiber cable 10 attached to the connector 1.
In FIG. 8, the optical fiber cable 10 is attached to the ferrule 19 via the fiber element 11 and the core wire 13. The fiber element 11 goes through the ferrule 19 and attached to the front end of the ferrule. The core wire 13 is inserted into and attached to the rear opening of the ferrule 19.
The connector 1 comprises a plug frame 20, a coil spring 30, a stop ring 40, a deformable ring 50, a pressure ring 60, an insulative hood 70, and a knob 80. These components are assembled in sequence at the front end of the optical fiber cable 10. The ferrule 19 attached to the optical fiber cable 10 is inserted into the plug frame 20 from back through an opening of an inner flange 21 until an outer flange 18 of the ferrule 19 abuts against the inner flange 21.
The coil spring 30 is placed between the outer flange 18 of the ferrule 19 and the stop ring 40 which is made from a metal to bias the ferrule 19 forwardly so that upon plugging, the ferrule 19 is movable in the axial direction.
The stop ring 40 is placed behind the plug frame 20 so as to cover the coil spring 30. The front section of the stop ring 40 is inserted into the rear opening of the plug frame 20. FIG. 9 shows the stop ring 40 and the plug frame 20. In order to connect the plug frame 20 and the stop ring 40, a pair of arcuate projections 41 are provided on the stop ring 40 while a pair of slots 22 are provided in the plug frame 20. When the front end of the stop ring 40 is inserted into the rear opening of the plug frame 20, the rear section of the plug frame 20 snaps the stop ring 40, with the arcuate projections 41 of the stop ring 40 are fitted into the slots 22 of the plug frame 20.
The deformable ring 50 made from aluminum is placed on the rear section of the stop ring 40, and the front section of the deformable ring 50 is cramped on the rear section of the stop ring 40. The braid 15 (FIG. 7(a) and (b)) is fixed between the deformable ring 50 and the stop ring 40. The rear section of the deformable ring 50 is reduced to provide a reduced section 51 over which the pressure ring 60 made from stainless or brass is placed and cramped. The sheath 17 (FIG. (a) and (b)) is fixed between the pressure ring 60 and the reduced section 51 of the stop ring 50.
The insulative hood 70 covers the deformable ring 50 and the pressure ring 60. A protruded edge 71 is provided on the front end of the insulative hood 70 so that when the insulative hood 70 is inserted over the deformable ring 50, the protruded edge 71 engages the front edge of the deformable ring 50 to prevent the insulative hood 70 from coming out of the deformable ring 50. The protruded edge 71 also is fitted in a circular groove in a middle section 44 of the stop ring 40 and engages a shoulder of a rear section 46 of the stop ring 40 to prevent the insulative hood 70 from coming out of the stop ring 40.
How to attach these connector components to the optical fiber cable 10 will be described with reference to FIGS. 7 and 8. As FIG. 7(c) shows, the insulative hood 70, the pressure ring 60, the deformable ring 50, the stop ring 40, and the coil spring 30 are attached in this order to the optical fiber cable 10. As FIG. 7(a) shows, the sheath 17 of the optical fiber cable 10 is removed to expose the fiber element 11, the core wire 13, and the braid 15. As FIG. 7(b) shows, the ferrule 19 is attached to the optical fiber cable 10 via the core wire 13 and fiber element 11.
As FIG. 8 shows, the ferrule 19 is inserted into the opening of the inside flange 21 of the plug frame 20. The coil spring 30 is placed into the rear opening of the plug frame 20 such that the front end of the coil spring 30 is held by the plug fame 20 via the ferrule 19 while the rear end of the coil spring 30 is held by the stop ring 40. The front end of the stop ring 40 is inserted into the rear opening of the plug frame 20 such that the arcuate projections 41 are fitted into the slots 22 of the plug frame 20. The braid 15 are arranged on the rear section of the stop ring 40 and the deformable ring 50 is placed on the stop ring 40 to hold the braid 15 and the deformable ring 50 is crimped. Then, the front end of the sheath 17 is placed on the reduced section 51 of the deformable ring 50 and the pressure ring 60 is moved to the right in FIG. 7 and crimped on the reduced section 51 of the deformable ring 50. Finally, the insulative hood 70 is moved to the right in FIG. 7 to cover the deformable ring 50 and rear section of the stop ring 40.
As FIG. 7(d) shows, the knob 80 is attached to the plug frame 20 by moving the knob 80 and the optical fiber cable in directions shown by arrows. As FIG. 8 shows, openings 81 are provided in the respective faces of the knob 80, and projections 25 are provided on the plug frame 20 (FIG. 9) to engage the openings 81 to fix the knob 80.
FIG. 10 shows a optical connector which the inventor has developed before. FIGS. 10(a) and (b) are an axial section and a top plan view of the connector. In FIG. 10(a), the axial section is shown above the central line while the side view of the connector 1 is shown below the central line. The optical fiber cable and ferrule are omitted from these figures. The components, structures, functions, and assembling of the connector are substantially the same as those of the conventional one except for those hereinafter described. Like components are given like reference numerals throughout the figures.
FIG. 11 shows a stop ring 40 of the connector of FIG. 10. FIGS. 11(a) and (b) are half-sections side and top views of the stop ring 40, respectively. The stop ring 40 is made from a metal by cutting.
Unlike the conventional one, the front section 42 of the stop ring 40 is provided with upper and lower arcuate projections 41 and a circular projection 47. As FIG. 10(a) shows, when the stop ring 40 is attached to the plug frame 20, the circular projection 47 is attached to the plug frame 20. An inside inclined face 27 is provided on the plug frame 20 from the slot 22 to the end of the plug frame 20 corresponding to the circular projection 47 so as to receive the circular projection 47 when the stop ring 40 is attached to the plug frame 20.
The rear section 46 of the stop ring 40 is provided with a knurl 49. As FIG. 12 shows, the rear portion 46 of a conventional stop ring 40 has a flat part because a complicated form cannot be made by cutting or, if possible, the cost is prohibitively high. Consequently, the rear section 46 has poor grip to the braid 15 (FIGS. 10(b) and (c)), and the braid is fixed by only the pressure of the deformable ring onto the knurl 49.
In FIG. 11, the intermediate section 44 between the rear section 46 and the front section 42 of the stop ring is provided with a reduced diameter having an even thickness to receive the inside projection 71 of the insulative hood (FIG. 10(a)). In this example, the inside projection 71 extends the entire circumference of the insulative hood.
Where the stop ring is made from a metal, it is necessary to use cutting for forming it, resulting in the high manufacturing cost. In addition, as the optical fiber cable becomes thin, the weight of a connector puts more burden on the optical fiber cable, causing the breakage of the optical fiber cable when it is attached to the connector.
Where the stop ring is made by molding, it is weaker than the metal one, causing breakage. In addition, it is necessary to reduce the crimping power to the stop ring, failing to prevent the braid from coming out of the stop ring and deformable ring. Where the rear portion of the stop ring is flat, the separation of the braid takes place more frequently.